Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.5.1.52 (PNGase F)
 1,527 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A new murine IgA mAb (JKT.M1), developed against Jurkat T cells chronically infected with HIV IIIB induces in vitro homotypic aggregation in several hemopoietic cell lines. The JKT.M1 Ag is expressed on a wide variety of cell types including human lymphocytes, monocytes, platelets, RBC, human umbilical vein endothelial cells, many T cell lines, myelomonocytic cell lines, and a primate kidney cell line. The JKT.M1 Ag shows differential expression on myelomonocytic cells; it is present on K562 and HL60 cell lines, which represent precursors of E and monocytes, respectively, but is not expressed on the surface of U937 and THP-1 cell lines, which appear to represent intermediate cell types of the monocytic cell lineage. However, the JKT.M1 Ag is expressed on mature peripheral blood monocytes and the MonoMac cell line. Immunoprecipitation from cell lysates (Jurkat, SupT1, PBMC, MonoMac) with the JKT.M1 mAb yields a 20-kDa Ag with few if any carbohydrate residues as determined by N-glycanase and neuraminidase treatments. The pI appears acidic by two-dimensional gel analysis, and the nonreduced form migrates more slowly than the reduced form when analyzed by SDS-PAGE suggesting the presence of intramolecular disulfide bridge(s). JKT.M1 mAb-induced cell adhesion is shown to be divalent cation- and temperature-dependent. The adhesion induced by JKT.M1 mAb is inhibited by 20 microM cytochalasin B and also by 2 mM 2-deoxyglucose plus 10 mM sodium azide suggesting that cytoskeletal changes and metabolic energy are required. Aggregation induced by JKT.M1 appears to be independent of CD43, CD44, and VLA4 (CD29/CD49d), mAb against which have also been shown to induce homotypic cell adhesion. Anti-CD18 mAb have been shown to inhibit homotypic aggregation in other studies but failed to do so in the present study. Thus JKT.M1-induced adhesion also appears to be independent of CD18, the beta-chain of leukocyte integrins. However, like mAb against LFA-1, immobilized JKT.M1 stimulates a T cell line to undergo dramatic morphologic changes which could be enhanced by the addition of phorbol ester. These data suggest that the novel 20-kDa molecule recognized by the JKT.M1 mAb may trigger cell adhesion through a previously undescribed mechanism.
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PMID:A monoclonal antibody against a novel 20-kDa protein induces cell adhesion and cytoskeleton-dependent morphologic changes. 138 18

Expression, saturation, and endocytosis of IgA Fc receptors (Fc alpha R) were analyzed in blood phagocytic cells of patients with alcoholic liver cirrhosis (ALC). Surface Fc alpha R expression was decreased in monocytes but not in neutrophils, as evaluated by IgA binding and anti-Fc alpha R mAb. The Fc alpha R of ALC patients were saturated by IgA1 and IgA2. ALC Fc alpha R had a higher M(r) (60 to 90 kDa) than those of controls (55 to 75 kDa) with a similar 32-kDa protein core after N-glycanase treatment, suggesting the expression of Fc alpha R molecules with altered carbohydrate moieties. Treatment of U937 cells with IFN-gamma induced a decrease of surface Fc alpha R expression in a dose-dependent manner, with a similar M(r) as observed for ALC patient Fc alpha R (60 to 90 kDa). Fc alpha R endocytosis was induced by anti-Fc alpha R or IgA. Neutrophils internalized Fc alpha R molecules faster than did monocytes. Endocytosed Fc alpha R co-localized with cathepsin D, suggesting an endolysosomal compartment pathway. In ALC monocytes, Fc alpha R endocytosis was defective, with nearly 50 to 60% of receptors detected on the cell surface even after 90 min at 37 degrees C. Similarly, delayed Fc alpha R endocytosis was observed on IFN-gamma-treated U937 cells as compared with PMA-activated cells. Defective internalization of surface-bound IgA with reflux of IgA to cell surface was also observed on ALC monocytes, but not on normal cells preincubated with patients' plasma, ruling out direct effects of IgA. The inverse correlation between monocyte Fc alpha R levels and serum IgA levels associated with defective endocytosis suggest that altered Fc alpha R expression might contribute to receptor saturation and generation of increased plasma levels of IgA and IgA-immune complexes in ALC patients.
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PMID:Altered expression of monocyte IgA Fc receptors is associated with defective endocytosis in patients with alcoholic cirrhosis. Potential role for IFN-gamma. 763 20

In contrast to antigen-antibody complexes containing native human IgA, solid-phase-deposited IgA activates the alternative complement pathway and binds C3b. To investigate the role of carbohydrate chains in this, various human IgA preparations were treated with neuraminidase alone or together with N-glycanase or O-glycanase, or with mixed glycosidases from the oral bacterium, Streptococcus mitis. Depletion of oligosaccharides was determined by carbohydrate analysis. Removal of sialic acid and N-linked glycan chains greatly increased the C3b-fixing properties of normal serum IgA1 and IgA2. Myeloma IgA1 and IgA2 proteins and secretory IgA had higher C3b-binding activity than normal serum IgA, and this was further increased by removal of sialic acid and N-linked glycans. Fc alpha and Fc alpha-SC fragments of myeloma and secretory IgA1, respectively, but not Fab alpha fragments, obtained by cleavage with bacterial IgA1 proteases and also free secretory component, fixed C3b by the alternative pathway.
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PMID:The role of the carbohydrate chains in complement (C3) fixation by solid-phase-bound human IgA. 792 4

One of the hallmarks of mucosal-host defense is the clearance of inhaled Ags by alveolar macrophages (AM) through interactions of IgA Abs and IgA Fc receptors (Fc alpha R). AM constitutively expressed Fc alpha R at lower levels than freshly isolated and in vitro-differentiated monocytes as determined by immunofluorescence using four anti-Fc alpha R mAb. SDS-PAGE analysis of iodinated cell surface proteins revealed that Fc alpha R on AM has an Mr of 50 to 65 kDa, slightly lower than that on monocytes (55-75 kDa). Treatment of AM Fc alpha R by N-glycanase gave rise to a protein core of 28 KDa, smaller than the 32-kDa backbone of blood monocytes. AM Fc alpha R molecules were unaffected by phosphatidylinositol-phospholipase C treatment. Fc alpha R transcripts were analyzed by reverse transcription-PCR using primers in the 5' and 3' regions of a U937 Fc alpha R cDNA. Three transcripts were amplified, cloned, and sequenced from AM and/or monocyte mRNA, the full length Fc alpha R and two alternatively spliced products corresponding to deletions of 66 and 288 nucleotides in the portion coding for the extracellular domain; they were named Fc alpha R a.1, a.2, and a.3, respectively. These PCR products were transcribed and translated in vitro into three proteins (Mr 32, 30, and 22 kDa, respectively), in which the 32- and 30-kDa species were immunoprecipitated by an anti-Fc alpha R mAb. The predicted size of the protein encoded by the Fc alpha R a.2 transcript without the leader peptide is Mr approximately 27,400, a value that is consistent with the Mr of AM Fc alpha R backbone. These results indicate that AM express at their surfaces a protein product of an alternatively spliced Fc alpha R transcript, the Fc alpha R a.2 isoform, that might have physiologic relevance in IgA-mediated host defense at mucosal sites.
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PMID:Identification of Fc alpha receptor (CD89) isoforms generated by alternative splicing that are differentially expressed between blood monocytes and alveolar macrophages. 866 19

Calves with naturally acquired Dictyocaulus viviparus infection mount an effective immune response. In the search for protection-inducing antigens, we found that several D. viviparus third-stage larval (L3) and adult ES products carry N-glycans. Deglycosylation of the worm antigens using PNGase F resulted in reduced IgA, IgE, IgG1 and IgG2 (but not IgM) reactivities in sera of primary infected animals, suggesting that the carbohydrate moieties contained immunodominant epitopes. Challenge infection resulted in increased specific serum antibody levels against ES and L3 in the re-infected and challenge control groups. Testing of sera by enzyme-linked immunosorbent assay (ELISA) demonstrated a significant increase in IgG1 and IgE (but not IgA or IgG2) reactivity against the deglycosylated antigens in the re-infected group compared with the challenge control group. Sera from calves vaccinated with irradiated larvae showed a strong anti-N-glycan response, but no booster response against the protein backbone after challenge infection, consistent with the absence of a memory response. Together, our results suggest that D. viviparus proteins carry immunodominant N-glycan moieties that elicit a strong but short-lived immune response during infection and after vaccination, whereas the protein backbones effectively induce a memory response which results in a long-lasting, potentially protective immune response in re-infected, but not in vaccinated calves.
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PMID:Differential N-glycan- and protein-directed immune responses in Dictyocaulus viviparus-infected and vaccinated calves. 1703 77